Exhaust System Replacement

Tynan918

Royal Smart Person
Thread starter
Aug 2, 2021
1,086
63
Never replaced manifolds, installed headers, or any exhaust parts...removed exhaust manifolds for a engine pull once and wrapped headers before, but that's it when it comes to the exhaust system.

Should I buy the parts and have a shop install them (how much ?) or just install everything myself

Starting with the manifolds first...

Headers or OEM manifolds? If headers, can you give me examples or specs as to what I should be looking for while shopping for headers ?

IMG_20220910_165323997.jpg
 

79 USA 1

G-Body Guru
Sep 2, 2011
951
93
Cheektowaga, New York
And the only gaskets I can find locally with a seventh hole are these...
View attachment 208466


Those gaskets should work fine. Make sure you clean both the head surface and the manifold surfaces before installing. My Dad taught me a trick used back in the 50's & 60's that I still use today with stock manifolds and that is to put a thin smear of anti seize or even wheel bearing grease on the mating surfaces or if using gaskets very lightly coat the gaskets then install them. I've never has a failure with stock manifolds and I normally run them without the gaskets.
Next, the manifolds you have for your car should look like these below.

Manifolds.jpg
The crossover pipe should mount directly to the ball flange on the driver side. No spacers no seal.
The crossover pipe on the passenger side should mount to an EFE valve or at least the remains of it to give a mating ball to seal to. should look like below.

E1089.JPG
Inspect your crossover for any weak spots or holes, It will show up as black carbon streaks.
Having clean mounting surfaces on the head, manifolds, crossover and retightening the manifold bolts after a few heat cycles should give you a leak free front part of the exhaust system.
 
  • Useful
  • Like
Reactions: 1 users

Tynan918

Royal Smart Person
Thread starter
Aug 2, 2021
1,086
63
Those gaskets should work fine. Make sure you clean both the head surface and the manifold surfaces before installing.
Gotcha, thanks for the clarification. I'll hold off on this job, I didn't smell any exhaust fumes this morning on a 5 - 10 mile trip... it's not ticking or anything major either... it's the fuel economy, I thought switching from 87 to 91 would better my fuel economy, not only make my engine run better because it's said that 91 burns longer.

Maybe it's my fuel pressure or air fuel ratio.. Fuel pressure is at 6.5 psi, and I used a vacuum gauge to set my idle mixture screws...

Ignition timing is 12° before top dead cylinder and totaled at 36° before top dead cylinder, and once that was set in I advanced it without the timing light until it ran rough and retarded it until it stopped and left it there. My RPMs may be too high, idle RPM is 1000-1200 and in gear is 600-700.. the higher RPMs are after I have been driving and the lower is what it starts out from first starting it up.

Sometimes after warming up the engine in the morning if I put my foot down on it it hesitates/bogs and has stalled on me a few times, but doesn't do that after the first time.


Next, the manifolds you have for your car should look like these below.

Manifolds.jpg
The crossover pipe should mount directly to the ball flange on the driver side. No spacers no seal.
The crossover pipe on the passenger side should mount to an EFE valve or at least the remains of it to give a mating ball to seal to. should look like below.

E1089.JPG
Inspect your crossover for any weak spots or holes, It will show up as black carbon streaks.
Having clean mounting surfaces on the head, manifolds, crossover and retightening the manifold bolts after a few heat cycles should give you a leak free front part of the exhaust system.
My exhaust manifolds look just like that, naked and all.

I don't have a crossover pipe or an efe valve.. I'm assuming that's part of the emissions system and my emissions are gutted out.. no computer, no O2 sensors, no any of that.
 

79 USA 1

G-Body Guru
Sep 2, 2011
951
93
Cheektowaga, New York
I don't have a crossover pipe or an efe valve.. I'm assuming that's part of the emissions system and my emissions are gutted out.. no computer, no O2 sensors, no any of that.
Actually you should have both, The EFE valve or at least the housing from it should be attached to the exit of the passenger side manifold. The crossover pipe runs from the left manifold, under the oil pan and connects to the outlet of the right side manifold then back to the rest of your exhaust system. Normally into the cat converter but I recall you saying it has been straight piped.
 
  • Like
Reactions: 1 user

Tynan918

Royal Smart Person
Thread starter
Aug 2, 2021
1,086
63
Actually you should have both, The EFE valve or at least the housing from it should be attached to the exit of the passenger side manifold. The crossover pipe runs from the left manifold, under the oil pan and connects to the outlet of the right side manifold then back to the rest of your exhaust system. Normally into the cat converter but I recall you saying it has been straight piped.
Screenshot_20221011-074517-536.png
Screenshot_20221011-074541-448.png


I have nothing attached or connected to my exhaust manifolds...

Yes it's straight piped...
 

79 USA 1

G-Body Guru
Sep 2, 2011
951
93
Cheektowaga, New York
The pipe that connects both your manifolds then connects to the rest of your exhaust system is a crossover pipe. The photo below shows it ahead of the catalytic converter, running under the oil pan near the oil filter to connect at the outlet of the exhaust manifold.

Cross over.jpg
 
  • Like
Reactions: 1 user

Tynan918

Royal Smart Person
Thread starter
Aug 2, 2021
1,086
63
The pipe that connects both your manifolds then connects to the rest of your exhaust system is a crossover pipe. The photo below shows it ahead of the catalytic converter, running under the oil pan near the oil filter to connect at the outlet of the exhaust manifold.

View attachment 208729
Yes I have a crossover pipe. I just don't have the other things that you said that were attached to the exhaust manifolds. I see the stock setup on some used exhaust manifolds on eBay and that's not what I have at all, I have none of that.
 

scoti

Royal Smart Person
Supporting Member
Sep 5, 2019
1,642
113
Texas
Yes I have a crossover pipe. I just don't have the other things that you said that were attached to the exhaust manifolds. I see the stock setup on some used exhaust manifolds on eBay and that's not what I have at all, I have none of that.
It's very common that those items are removed over the years on vehicles that are worked on.
 

spidereyes455

G-Body Guru
Mar 6, 2013
708
93
Northeastern PA
Just a safety concern here. Your driver side front upper control arm bushing is VERY bad. And its likely the rest are too.
 
  • Agree
Reactions: 1 users

GBodyForum is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com. Amazon, the Amazon logo, AmazonSupply, and the AmazonSupply logo are trademarks of Amazon.com, Inc. or its affiliates.

Please support GBodyForum Sponsors

Classic Truck Consoles Dixie Restoration Depot Mike's Montes UMI Performance

Contact Admin@GBodyForum.com for info on becoming a sponsor